The present invention relates to an electrochromic formulation comprising a novel dye and an organic electrochromically switchable electronic component.
Electrochromic displays based on organic materials normally comprise an active electrochromic layer which, in the case of a display, is between two electrodes at right angles to one another. Essential constituents of the active layer are a redox system and a pH-active dye. The application of a voltage shifts the concentration ratio of the redox partners relative to one another within the material. This reaction releases or binds protons or ions within the material, which affects the pH. If a voltage is applied to the material, the shift in the equilibrium of the redox partners at the two electrodes runs in opposite directions. This leads to a rise in the pH at one of the electrodes, while it falls at the counter-electrode. A pH-active dye is then used to convert the change in the pH to a color change in the material, and to make the application of the voltage visible.
One way in principle of implementing electrochromic displays is to bring about the color change not by a change in the pH in the display but to use the redox processes which take place in any case, in order to generate high-contrast color change by the formation of reductive and/or oxidative states in suitable materials. In this context, the materials known as viologens and polythiophenes in particular have become known as material classes.
PCT/EP2006/064048 discloses corresponding dyes which have been found to be useful.
Electrochromically active formulations switch reversibly between two color states which are defined by the type of electrochromically active dye. For example, a dye based on a viologen structure is colorless in the unswitched state or white owing to the white pigment, but violet in the switched state.